Ignition device for combustion equipment



July 27, 1965 a. TOONE ETAL IGNITION DEVICE FOR COMBUSTION EQUIPMENT 2Sheets-Sheet 1 Filed June 28, 1962 July 27, 1965 B. TOONE ETAL IGNITIONDEVICE FOR- COMBUSTION EQUIPMENT 2 Sheets-Sheet 2 Filed June 28, 1962United States Patent 3,196,614 IGNITION DEVICE FOR COMBUSTION EQUIPMENTBrian Toone, Littleover, Derby, and Allan Michael Barham, Miclrleover,Derby, England, assignors to Rolls-Royce Limited, Derby, England, aBritish company Filed June 28, 1962, Ser. No. 206,003 Claims priority,application Great Britain, July 11, 1961, 25,147/61 6 Claims. (Cl.60-69152) This invention relates to combustion equipment, such forexample as is used in gas-turbine engines, of the class in which fuel isburnt in a stream of combustion supporting gas having an elevatedtemperature and flowing at high velocity.

The invention will be described hereinafter in its application togas-turbine engines. In such engines when employed for jet propulsionpurposes it is often necessary to eflect ignition in the jet pipe forreheat purposes.

According to the present invention, there is provided a' device adaptedto promote auto-ignition of fuel injected into the combustion-supportinggas stream, or to improve stability of combustion, or both, which devicecomprises a mass of refractory material and a foraminate element ofplatinum, or rhodium, or platinum/rhodium alloy or iridium or othersuitable metal having catalytic properties in promotion of combustion,the foraminate element comprising a portion in the form of a spiral rollwhich has a plurality of spaced convolutions and is located axially in aflow passage extending in the refractory mass between those surfacesthereof which in use face upstream and downstream in the gas stream.

The foraminate element may also include a portion in the form of a discat the downstream end of the flow passage and may further comprise aportion in the form of a disc at the upstream end of the flow passage.

According to a feature of this invention, in a construction having adisc portion at the downstream end of the flow passage, the disc portionmay be formed to a T- shape and the leg of the T-section inserted into aslot or notch in the refractory mass and the spiral roll portion.

In a preferred form, the foraminate element includes a tube which thespiral roll surrounds.

In one construction of device of this invention, the spiral roll of theforaminate element extends between upstream and downstream disc portionsand the refractory mass comprises a cylindrical part with the spiralroll in a bore extending through it and with the discs lying against itsend surfaces, a cup-shaped refractory casing housing the cylindricalpart and having a hole in its base coaxial with the bore of thecylindrical part and a refractory closure plate cemented to the end ofthe casing remote from its base, the closure plate having a hole in itco-axial with the bore.

In a second construction the foraminate element comprises a tube partand a downstream end disc welded to the tube and having a central holealigned with the tube bore, the spiral roll surrounding the tube part,and the refractory mass comprises a cup-shaped member housing the tubeand spiral roll and having the tube extending through a hole in itsbase, the discs lying against the external surface of the base, arefractory casing having a recess housing the cup-shaped member, acollar cemented in the open end of the recess to retain the cup-shapedmember and foraminate element in position, and a ring of refractorymaterial between the bottom of the recess and the disc, the collarhaving a hole registering with the tube bore and the casing having ahole extending from the bottom of the recess to the downstream surfaceof the casing.

3,196,614 Patented July 27, 1965 ice The operational value of acatalytic ignition device is assessed by the ranges over which operatingparameters efiecting ignition can be varied whilst obtainingsubstantially instantaneous ignition, that is ignition within a fewseconds of commencing fuel injection e.g. within 5 seconds. Anadditional characteristic of this device is that if the flame blows offthe gutter due to some transient instability, the catalyst causesimmediate re-ignition without any mechanical operation being required.One such parameter is the minimum temperature of the gas stream at whichignition can be effected satisfactorily. Another parameter is theminimum value of the fuel/air ratio at which ignition can be effectedsatisfactorily. Other parameters are the maximum Mach number and theminimum pressure at which satisfactory ignition can be achieved. It isfound that with the device of this invention, substantiallyinstantaneous auto-ignition can be achieved over ranges of gas pressure,gas temperature and of fuel/ air ratio which have low minimum values,and at relatively high Mach numbers. 7

Some embodiments of this invention will now be described with referenceto the accompanying drawings in which:

FIGURE 1 illustrates one form of catalytic device in axial section,

FIGURE 1A is a perspective view of part of the device shown in FIGURE 1,

FIGURE 2 is an exploded view of a second form of device,

FIGURE 3 illustrates in section a third form of catalytic device,

FIGURE 4 illustrates the use of devices according to this invention ingas turbine engine reheat equipment, and

FIGURE 5 is a detail illustration of part of FIG-- URE 4.

- num/rhodium foraminate material at high temperatures.

7 2) and when the catalytic element isin position the portion 12 extendsaxially through the length of the bore 11 The mass 10 has an axial bore11 extending through it from one end face to the other.

The device also comprises a catalytic element, conveniently formed fromgauze of a 20% Rh/ Pt alloy, and the catalytic element comprises aspiral roll portion 12, a downstream disc portion 13 which covers oneend face of the mass 10 and an upstream disc portion 14 which covers theother end face of the mass 10. The spiral portion 12 has a plurality ofspaced convolutions (FIGURE and is located therein for instance by ametal pin (not shown) extending transversely across the bore 11 andpassing through the convolutions of the spiral roll so pre 1 venting anytendency for the convolutions to telescope In use one or more of thesedevices are mounted in a stabilising gutter 20, so that the plate 17projects beyond the convex side of the gutter, which is usually aV-section ring, and the ,base of the casing projects into the concavityof the gutter. The plane of the disc portion 13 may be located at anypoint inside the convex side of the gutter, upstream of the planecontaining the down-stream edges of the gutter.

The gas stream flows from left to right as seen in the drawing anddesirably the fuel is injected in the upstream direction into the gasstream at a point which is a selected distance upstream of the gutter;If the fuel injector is too close to the gutter inadequate mixing of thefuel and gas occurs before the mixture reaches the ignition device.Under these conditions rapid lights may not be achieved.

Part of the fuel/air mixture flows through the passage formed by thebore 11 and in so doing flows over the catalytic element 12, 13, 14 andis ignited. The device is found to have good auto-ignitioncharacteristics.

In experiments, a device according to FIGURES 1 and 2 was constructedand it had the following dimension-s.

The casing 15 had an outside diameter of 1.375 inches, and an insidediameter of 1.00 inch, and the device had an overall length of 1.09inches.

The spiral roll of the catalytic element had a length of 0.90 inch and adiameter of 0.5 inch, there being six convolutions. The catalyticelement was made from Rh/Pt gauze of 0.010 inch thickness, and had amesh size of 36 meshes/inch.

Theh'ole 14 had a diameter of 0.218 inch and the hole .13 a diameter of0.25 inch.

The plane of the disc portion 13 stream of the gutter lips.

In a first series of experiments, the fuel injector had an orifice of0.038 inch in diameter and sprayed upstream and was placed at varyingdistances between 7 inches and 20 inches upstream of the device, andinstantaneous lights were obtained with gas temperatures varying between350 C. and 600 C., with fuel/ air ratios varying between 0.008 and,0.035 (the maximum limit obtainable with the fuel pump used) and withgas flows between Mach numbers 0.1 and 0.26. Weak extinction occurredsubstantially uniformly at a fuel/air ratio of 0.004 and wassubstantially independent of temperature.

In a secondseries of experiments with the same device, with the injector14 inches upstream of the device and with gas speeds between Machnumbers 0.25 and 0.5, instantaneous lights were obtained up to aboutMach number 0.4. 1

In further experiments, a device was used with the following dimensionsaltered.

The spiral roll portion was 0.500 inch in diameter and hadeightconv-olutions, the hole 13 was 0.375 inch in diameter, and the hole 140.300 inch in diameter.

This device gave instantaneous lights at gas flows of Mach number 0.45for gas temperatures down to 350 C. and for fuel/ air ratios between0.005 and 0.03. For gas flows of Machnumber 0.5 instantaneous lightswere obtained down to temperatures of 400 C. and effective lights downto 350 C.

In further experiments, the disc portion 13 was made from 0.020 inchthick gauze and good auto-ignition was obtained with added strength ofthe portion 13. i

The form of device shown in FIGURE 2 is similar to that in FIGURES 1 and1A and like parts are indicated by like references. 7

Instead of a plane disc portion 13, the downstream portion 113 is foldedto a T shape, the limbs 113a of the fold being welded together, and adiametral slot 114 is provided .in the mass 10 and the spiral rollportion 12 to receive the told. This device is intended to was 0.25 inchupstrengthen the disc at high temperature without reducing the gas iflowthrough the catalyst. To prevent the catalytic roll from pressing on thedownstream plate, a locating pin, shown at 115 is used. I

This arrangement gives added strength to the downstream portion 113 soincreasing the operational life of the device.

In an experiment, a device of this construction having themodified-dimensions above set forth was subjected i to an endurance testcomprising lighting tests at 400 C. and Mach number 0.4 and fuel/airratios of 0.015, a continuous run of twenty minutes with reheat at afuel/ air ratio of 0.025, and a continuous run at 750 C. without reheat.This cycle was repeatedand after 10 hours no vital damage to thecatalytic element, was found.

In another test simulating normal and reheat operation, no deteriorationof the catalytic element was observed afer 60 hours normal operation and6 hours reheat operation.

In the construction shown inFIGURE 3, the device comprises a foraminatecatalytic element which consists of a central tube 20 of expandedcatalytic metal, for example 0.020 inch thick expanded rhodium/platinumalloy containing 20 rhodium, a downstream end disc 21 of like material,the disc being welded to the end of the central tube 20 and having acentral hole 21a aligned with the bore of the tube 20, and surroundingthe tube 20 a spiral roll 22 of a similar catalytic metal, which is say0.010 inch thick the convolutions of the roll being spaced apart. Thecatalytic element also has an upstream gauze disc 27. The disc may befolded to a T-shape, the leg 27a of the T being inserted in a transverseslot in the tube 20 and the oonvolutions of the roll 22. The disc 27conducts heat from the catalytic zone to the relatively cool gasesentering the flow pas sage, and the folded arrangement when use-dincreases both the mechanical strength and the rate of heat transfer tothe relatively cool gases.

The catalytic element is housed in a flow passage extending in arefractory mass which comprises a cupshaped alumina member 23 receivingthe roll 22 and main portion of the tube 20, the member 23 having a holein its base 23a through which the tube 20 extends, the disc 21 lyingagainst the external surface of the base 23a. The members 23 isreceived. in a recess 24a extending inthe direction of gas flow from theupstream face of a refractory casing 24, there being a hole 24b,extending from the bottom of the recess to the downstream face of thecasing 24, the hole 24b being of larger diameter than the hole 21a. Aring of alumina 25 separates the disc 21 from the base of the casing 24.A collar 26 of alumina is cemented into the open end of the recess 24ato retain the member 23 and the catalytic element in position, thecollar 26 having a central hole 26a of the same diameter as the bore ofthe tube 20.

In an experiment, a device of this construction had the followingdimensions. The casing 24 had an outside diameter of 1.375 and an insidediameter of 1.00, and the device had an overall length of 1.09. Thespiral roll of the cataytic element had a length of 0.9" and a diameterof 0.5", there being 4 convolutions. The catalytic element was made from20% Rh/Pt gauze of 0.010" thickness. The mesh size was 36 per inch.

The centre tube had a diameter of /4" and was made from 20% Rh/Pt gauzeof 0.020" thickness. The mesh size was about 36 per inch.

The collar 26 was made from 20% Rh/Pt material in 0.020" thickness. Thehole 26a had a diameter of 3 and a downstream hole 26b had a diameter of0.375.

The fuel injector had an orifice of 0.038 in diameter, and sprayedupstream at a distance of 14" upstream of the device.

Instantaneous lights were obtained with gas temperatures between 350 C.and 600 C. with fuel/air ratios varying between 0.008 and 0.035, andwith gas flows between Mach numbers of 0.1 and 0.5.

A number of devices of this type have also been located in an enginereheat gutter and gave satisfactory lights down to 400 C. (lower limitsat which tests were carried out).

In a further device, a marked increase in mechanical reliability wasachieved by a number of modifications to the catalytic element shown inFIGURE 3. The tube 20 was increased to 0.375 diameter and was made from0.030" thick mesh in 20% Rh/Pt with meshes/inch. The plate 21 was madein solid Rh/Pt alloy and was welded to the tube. To restore the catalystzone to its original volume the internal bore of cup 23 was increased todiameter. The quantity of platinum/rhodrum alloy in the catalytic spiral22 was unchanged.

In an experiment with this device, the fuel injector had an injectionhole 0.038" in diameter and was located 14 upstream of the catalyst.Instantaneous lights were obtained with gas flows between Mach numbers0.1 and 0.5 and with gas temperatures above 340 C. and with fuel/airratios between .005 and 0.03.

The device has good auto-ignition and combustion stabilisingcharacteristics and is robust giving a good operational life.

In yet another construction, suitable for multigutter stabilisers of gasturbine reheat systems, two or more catalytic elements as abovedescribed are located in bores in a rectangular refractory mass. Such adevice is found to have good auto-ignition characteristics.

Instead of mounting the ignition devices as above described in thestabilising gutter, for instance as shown in FIGURE 1, one or more ofsuch devices may be mounted in bores in a radially-extending strutjointing two concentrically-arranged gutters, or in a plurality of suchstruts.

Such an arrangement is shown in FIGURES 4 and 5 which illustrates reheatequipment in the jet pipe of a gas turbine engine. The reheat equipmentcomprises a spider support 31 mounted in the jet pipe 30, annular reheatfuel manifolds 32 feeding fuel to injectors 33 the manifolds beingsupported by struts 34 mounted on the spider 31, and a flame stabilisercomprising an outer annular gutter 35 supported by struts 36 from thespider 31 and an inner annular gutter 37 which is connected to thegutter 35 by angularly spaced V-section sheet metal struts 38. Thestruts 38 each house one or more catalytic elements as above described.For instance in FIGURE 4, each strut 38 houses two catalytic devices 39,such as are shown in FIGURE 3, and in FIGURE 5 a strut 38 is shownhousing a single catalytic device 40 having two radially spaced flowpassage 4012 each housing a catalytic element. Clearly the base of thestrut 38 has holes 38a in it registering with the inlet ends of the flowpassages of the catalytic device, or devices. The catalytic devices areretained in position by indenting the sides of the strut 38 into grooves40a in the casing of the catalytic element 40 and by angle-section metalstrips 42 and top and bottom retaining plate 43 which are welded on tothe strut.

We claim:

1. A prime mover ignition device adapted to promote auto-ignition offuel injected into a combustion supporting gas stream, or to promotecombustion stability, or both, comprising a mass of refractory materialand a foraminate element of platinum, or rhodium, or iridium, or alloysof these, or other suitable metal having catalytic properties inpromotion of combustion, the foraminate element comprising a portion inthe form of spiral roll which has a plurality of spaced convolutions andis located axially in a flow passage, extending in the refractory massbetween those surfaces thereof which in use face upstream and downstreamin the gas stream and a portion in the form of a disc at the downstreamend of the flow passage, the disc portion at the downstream end beingformed to a T-shaped and the leg of the T-section being inserted into aslot or notch in the refractory mass and the spiral roll portion.

2. A prime mover ignition device adapted to promote auto-ignition offuel injected into a combustion supporting gas stream, or to promotecombustion stability, or both, comprising a mass of refractory materialand a foraminate element of platinum, or rhodium, or iridium, or alloysof these, or other suitable metal having catalytic properties inpromotion of combustion, the foraminate element comprising a portion inthe form of spiral roll which has a plurality of spaced convolutions andis located axially in a flow passage, extending in the refractory massbetween those surfaces thereof which in use face upstream and downstreamin the gas stream, a tube which the spiral roll surrounds, and anupstream plate which is folded to a T-shape to increase mechanicalstrength and also to increase the amount of heat transferred to theincoming gas mixture.

3. A prime mover ignition device adapted to promote auto-ignition offuel injected into a combustion supporting gas stream, or to promotecombustion stability, or both, comprising a mass of refractory materialand a foraminate element of platinum, or rhodium, or iridium, or alloysof these, or other suitable metal having catalytic properties inpromotion of combustion, the foraminate element comprising a portion inthe form of spiral roll which has a plurality of spaced convolutions andis located axially in a flow passage, extending in the refractory massbetween those surfaces thereof which in use face upstream and downstreamin the gas stream, the spiral roll of the foraminate element extendingbetween upstream and downstream disc portions, the refractory masscomprising a cylindrical part with the spiral roll in a bore extendingthrough it and with the discs lying against its end surfaces, acup-shaped refractory casing housing the cylindrical part and having ahole in its base co-axial with the bore of the cylindrical part and arefractory closure plate cemented to the end of the casing remote fromits base, the closure plate having a hole in it co-axial with the bore,the downstream disc being folded to a T-shape, the limbs of the foldbeing welded together and being inserted in a diametral slot in thecylindrical part and the spiral roll.

4. A prime mover ignition device adapted to promote auto-ignition offuel injected into a combustion supporting gas stream, or to promotecombustion stability, or both, comprising a mass of refractory materialand a foraminate element of platinum, or rhodium, or iridium, or alloysof these, or other suitable metal having catalytic properties inpromotion of combustion, the foraminate element comprising a portion inthe form of spiral roll which has a plurality of spaced convolutions andis located axially in a flow passage, extending in the refractory massbetween those surfaces thereof which in use face upstream and downstreamin the gas stream, the spiral roll of the foraminate element extendingbetween upstream and downstream disc portions, the refractory masscomprising a cylindrical part with the spiral roll in a bore extendingthrough it and with the discs lying against its end surfaces, acup-shaped refractory casing housing the cylindrical part and having ahole in its case co-axial with the bore of the cylindrical part and arefractory closure plate cemented to the end of the casing remote fromits base, the closure plate having a hole in it coaxial with the bore,and a metal retaining pin extending across the bore of the cylindricalpart and through the convolutions of the spiral roll to retain thespiral roll within the bore.

5. A prime mover ignition device adapted to promote auto-ignition offuel injected into a combustion supporting gas stream, or to promotecombustion stability, or both, comprising a mass of refractory materialand a foraminate element of platinum, or rhodium, or iridium, or alloysof these, or other suitable metal having catalytic properties inpromotion of combustion, the foraminate element comprising a portion inthe form of spiral roll which has a plurality of spaced convolutions andis located axially in a flow passage, extending in the refractory massbetween those surfaces thereof which in use face upstream and downstreamin the gas stream, the foraminate element further comprising an upstreamdisc, a tube part and a downstream end disc welded to the tube andhaving a central hole aligned with the tube bore, the

spiral roll surrounding the tube part, and the refractory masscomprising a cup-shaped member housing the tube and spiral roll andhaving the tube extending through a hole in its base, the downstream enddisc lying against the external surface of the base, a refractory casinghaving a recess housing the cup-shaped member, a collar cemented in theopen end of the recess to retain the cupshaped member and foraminateelement in position, and a ring of refractory material between thebottom of the recess and the disc, the collar having a hole registeringwith the tube bore and the casing having a hole extending from thebottom of the recess to the downstream surface of the casing.

6. A device according to claim 5, the upstream disc being folded to aT-shape, the leg of the T being inserted in a transverse slot in thetube and in the convolutions of the spiral roll.

References Cited by the Examiner UNITED STATES PATENTS Williams et a1.

DONLEY J. STOCKING, Primary Examiner. ABRAM BLUM, SAMUEL LEVINE,Examiners.

1. A PRIME MOVER IGNITION DEVICE ADAPTED TO PROMOTE AUTO-IGNITION OFFUEL INJECTED INTO A COMBUSTION SUPPORTING GAS STREAM, OR TO PROMOTECOMBUSTION STABILITY, OR BOTH, COMPRISING A MASS OF REFRACTORY MATERIALAND A FORAMINATE ELEMENT OF PLATINUM, OR RHODIUM, OR IRIDIUM, OR ALLOYSOF THESE, OR OTHER SUITABLE METAL HAVING CATALYTIC PROPERTIES INPROMOTION OF COMBUSTION, THE FORAMINATE ELEMENT COMPRISING A PORTION INTHE FORM OF SPIRAL ROLL WHICH HAS A PLURALITY OF SPACED CONVOLUTIONS ANDIS LOCATED AXIALLY IN A FLOW PASSAGE, EXTENDING IN THE REFRACTORY MASSBETWEEN THOSE SURFACES THEREOF WHICH IN USE FACE UPSTREAM AND DOWNSTREAMIN THE GAS STREAM AND A PORTION IN THE FORM OF A DISC AT THE DOWNSTREAMEND OF THE FLOW PASSAGE, THE DISC PORTION AT THE DOWNSTERAM END BEINGFORMED TOA T-SHAPED AND THE LET OF THE T-SECTION BEING INSERTED INTO ASLOT OR NOTCH IN THE REFRACTORY MASS AND THE SPIRAL ROLL PORTION.